This invention pertains to test equipment for electronic circuits and is particularly concerned with a novel digital readout test probe which is especially useful in providing a decimal readout of a binary coded decimal signal appearing at selected terminal pins of an integrated circuit.
In designing, developing, testing and/or repairing digital electronic circuits, it is useful for the technician or engineer to know the condition of signals at selected test points of the circuits. With the increasing use of microelectronic devices in digital circuits, it is important that test equipment for such digital circuitry provide maximum utility and convenience to the person using the equipment. Because present digital circuit technology operates with binary type logic signals, testing of other than the simplest circuit can be a time consuming procedure. Moreover, with the miniaturized microcircuitry, the task of physically making an electrical connection with a desired test point on the circuit can be difficult.
A number of prior testing devices of the type to which the present invention relates are known in the art. A novelty search in the United States Patent Office conducted in connection with the present invention developed the following U.S. patents which show illustrative test probes: U.S. Pat. Nos. 3,300,718; 3,667,037; 3,670,245; 3,750,015; 3,761,808; 3,810,012; 3,870,953; and 3,882,386. One problem with prior test equipment is that it is incapable of quickly and reliably presenting information as to the condition of the digital circuit signals in a form which is readily intelligible to the user of the test equipment. Another problem is that it is generally not compatible with the many different types of specific digital integrated circuits which are now on the market.
Accordingly, the present invention is directed to a novel and extremely useful digital readout test probe for use by electronic technicians and engineers in designing developing, testing and/or repairing systems incorporating digital circuits. One feature of the present invention is that it is directly compatible with various types of microcircuits including DTL, TTL, and CMOS type systems. The probe contains its own power supply and possesses extremely high input impedance, and thus, cannot load down the digital circuits under test. Moreover, the probe can accept input signals over the voltage ranges customarily prevailing in present digital circuits.
Another feature of the invention is that it provides a digital decimal display representative of a binary coded decimal signal present in the circuit under test. This is important in that information as to the performance of the digital circuitry under test is readily displayed in an intelligible form to the user of the probe.
A further feature of the invention is that the probe can be programmed to monitor data for any possible pin configuration in an integrated circuit under test. Connection to the circuit under test is via a clip-on type connector which is coupled via color coded lead wires to a converter circuit which drives the decimal readout display. The lead wires terminate in hollow terminal connector pins which may be mated with selected conductor pins on the connector in accordance with the pin configuration of the integrated circuit under test. This is important in providing maximum versatility and operator convenience so that even in complicated digital circuits containing numerous different types of integrated circuit devices, testing can be accomplished with a single piece of equipment which is readily programmed according to each specific device under test.
Ancillary features of the present invention include its compact size permitting portability and use in close quarters; a self-test feature for testing the operability of the probe circuitry and display; and color coding for each lead wire according to the significance of the digital signal conducted thereby.